<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>封装ajax</title>
</head>
<body>
    <script>
function ajax(url){
    return new Promise((resolve,reject)=>{
        let xhr =new XMLHttpRequest()
        xhr.open('get',url)
        xhr.send()
        xhr.onreadystatechange=function(){
            console.log(xhr);
            if(xhr.readyState==4){
                if(xhr.status >=200 && xhr.status < 300){
                   let res=JSON.parse( xhr.responseText)
                      resolve()
                } else{reject(xhr.responseText)}          
             }
        }
    })
}


ajax('./01.json').then((res)=>{
    console.log(res);
})
.catch((error=>{
    console.log(error)
}))









    </script>












</body>
</html>